In many examples of drilling for oil or gas wells with standard U.S. technology, a drive bushing is turned by a rotary table. The drive bushing has a square or hexagonal passage therethrough slidably receiving a long square or hexagonal member known as a kelly. One potential hazard in drilling for oil or gas is encountering pressures which are not balanced by drilling fluid in the hole. One of many safety devices are valves on the kelly, on the lower end immediately above the uppermost drill pipe joint and on the upper end between the kelly and the swivel. The idea is to actuate the blowout preventer to seal around the outside of the drill string and to close the kelly valve or valves to keep well fluids from returning through the drill string. An analogous valve, known as a safety valve, is used in analogous situations in completion and workover operations.